Method and device for electronically controlling the beating of a heart using venous electrical stimulation of nerve fibers

ABSTRACT

An electro-stimulation device includes a pair of electrodes for connection to at least one location in the body that affects or regulates the heartbeat. The electro-stimulation device both electrically arrests the heartbeat and stimulates the heartbeat. A pair of electrodes are provided for connection to at least one location in the body that affects or regulates the heartbeat. The pair of electrodes may be connected to an intravenous catheter for transvenous stimulation of the appropriate nerve. A first switch is connected between a power supply and the electrodes for selectively supplying current from the power supply to the electrodes to augment any natural stimuli to the heart and thereby stop the heart from beating. A second switch is connected between the power supply and the electrodes for selectively supplying current from the power supply to the electrodes to provide an artificial stimulus to initiate heartbeating. In another aspect, the invention is directed to a method for arresting the beat of a heart in a living body comprising the steps of connecting the pair of electrodes to at least one location in the body that affects or regulates the heartbeat and supplying an electrical current to the electrodes of sufficient amplitude and duration to arrest the heartbeat. The device may also serve to still the lungs by input to a respirator or by stimulation of the phrenic nerve during surgical procedures.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods and devices for controlling theoperation of the human heart or other organs by means of electricalstimulation, and more particularly, to devices for electronicallyslowing or stopping the heart.

2. Description of the Related Art

In some surgical procedures, such as coronary bypass surgery, it isnecessary to stop the heart from beating so that the surgeon can performnecessary techniques. The use of a cardioplegia solution to stop theheart from beating without rerouting the blood would permit the surgeonto accomplish the required task without interference from heartmovement. However, this is not a viable approach, since the body needs aconstant supply of oxygen. Thus, there exists a need to temporarily slowdown or stop heart movement during minimally invasive CABG or othersurgical procedures to permit the surgeon to accomplish the requiredtask. In the context of treatment of the heart by means of implantedmedical devices, such as pacemakers, defibrillators and drug dispensers,it is also sometimes beneficial to slow or temporarily stop the heart,either for diagnostic or therapeutic purposes.

It has been known in the past to stimulate the vagal nerves byinvasively dissecting the major nerve bundle and placing a spiral orenveloping nerve-type cuff around the nerve bundle. The nerve fibers arethen directly stimulated by electrical field to achieve reduction inepilepsy, heart rate slowing, and potential blood pressure changes. In astudy entitled "Selective Stimulation of Parasympathetic Nerve Fibers tothe Human Sinoatrial Node", Circulation, Vol. 85, No. 4, April 1992, itwas reported that cardiac parasympathetic nerve fibers located in anepicardial fat pad at the margin of the right atrium, the superior venacava, and the right pulmonary vein in humans could be electricallystimulated to affect the heart rate. Additional reference is found inPACE October 1992 Vol. 15, No. 10, pt. 11, pages 1543-1630 on the use ofnerve cuff stimulation of the vagal nerves (left side) in humans forreduction of epilepsy and it's side-effects. Additional uses forelectrical nerve stimulation have been disclosed for the prevention ofarrhythmias, alteration of hemodynamics, stimulation of the hypoglossalnerve for sleep apnea, stimulation of the stomach, and control of thesphincter for bladder or colon evacuation.

Currently, only nerve cuff-type electrodes or impalement-type electrodesare used for nerve stimulation, other than in the spinal cord. Thesetypes of electrodes can potentially cause irreversible nerve damage dueto swelling or direct mechanical damage of the nerve. The placement ofthese electrodes either around the nerve bundle or into the neuralperineum also poses a significant risk. The electrode placement isusually performed through very invasive surgery which in and of itselfproduces a high risk to nerve damage, and would be self-defeating whenperforming minimally invasive surgery. However, it has been demonstratedthat the paraympathetic nerve fibers associated with the heart can alsobe stimulated by means of electrodes located on transvenous leads, as inU.S. Pat. No. 5,243,980, issued to Mehra et al, U.S. Pat. No. 5,507,784,issued to Hill et al and U.S Pat. No. 5,356,425, issued to Bardy et al.The use of transvenous electrode leads to stimulate parasympatheticnerves associated with the heart is also discussed in the article"Neural effects on Sinus Rate and Atrial Ventricular Conduction Producedby Electrical Stimulation From a Transvenous Electrode Catheter in theCanine Right Pulmonary Artery, by Cooper et al., published inCirculation research, Vol. 46, No. 1, January 1980, pp. 48-57.

In conjunction with spinal cord stimulation, electrodes or electrodearrays located on pliant electrode pads are often employed. Recently,the ability to select from among various pairs of electrodes located onsuch electrode pads has been proposed to allow steering of theelectrical field produced by the electrodes, as in U.S. Pat. No.5,501,703, issued to Holsheimer, incorporated herein by reference in itsentirety. Such electrode arrays offer additional possibilities tostimulate nerve fibers without direct and possibly damaging contact.

SUMMARY OF THE INVENTION

It is with these problems in mind that a new apparatus and method havebeen developed for electrically stimulating or destimulating certainnerves associated with the functioning of the heart or other organswhich can be combined with certain surgical procedures or incorporatedinto implantable medical devices. According to one aspect of theinvention, the invention is embodied in an electro-stimulation deviceincludes at least two electrodes for connection to at least one locationin the body that affects or regulates the heartbeat. At least one switchis connected between a power supply and the electrodes for selectivelysupplying current from the power supply to the electrodes to augment thenatural stimuli to the heart in order to control the beating of theheart, and preferably to stop the heart from beating. Preferably, theswitch is a foot switch operable by a surgeon to free a surgeon's handsduring surgery.

According to another aspect of the invention, the at least twoelectrodes are connected to an intravenous catheter for transvenousstimulation/destimulation of the heartbeat.

According to another feature of the invention, an electro-stimulationdevice for both electrically destimulating and stimulating the heartincludes a pair of electrodes for connection to at least one location inthe body that affects or regulates the heartbeat. A first switch isconnected between a power supply and the electrodes for selectivelysupplying current from the power supply to the electrodes to augment thenatural stimuli to the heart and thereby stop the heart from beating. Asecond switch is connected between the power supply and the electrodesfor selectively supplying current from the power supply to theelectrodes to provide an artificial stimulus to initiate the heartbeat.

In a further aspect of the invention, a method for arresting the beat ofa heart in a living body includes the process of connecting a pair ofelectrodes to at least one location in the body that affects orregulates the heartbeat and supplying an electrical current to theelectrodes of sufficient amplitude and duration to arrest the heartbeat.According to one aspect of the invention, the step of supplying anelectrical current to the electrodes includes supplying an alternatingcurrent.

In yet further aspects of the invention, the invention is embodied in anexternal or implantable device which employs electrodes located ontransvenous leads located in veins adjacent nerve fibers to bestimulated. in these aspects of the invention, the leads preferablycarry an array of electrodes from which pairs of electrodes can bechosen in order to direct the electrical field appropriately withrespect to the desired nerve fibers.

It is to be noted that with regard to the effect of the delivered nerveor other stimulus pulses relative to the action of the heart the phrase"stimulate the heart" and its derivatives as used herein refer to theinitiation of the heartbeat through the application of electricity,while the phrase "destimulate the heart" and its derivatives refer tostopping or arresting the heartbeat through the application ofelectricity.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawings inwhich:

FIG. 1 is a perspective view of an electro-stimulation device accordingto the present invention;

FIG. 2 is a perspective view of an electro-stimulation device accordingto a second embodiment of the present invention;

FIG. 3 is a schematic diagram of a circuit for use with theelectro-stimulation device of FIGS. 1 and 2;

FIG. 4 is a diagrammatical view of a pair of electrodes of theelectro-stimulation device attached to a pair of points on the heart;

FIG. 5 is a diagrammatical view of a pair of electrodes of theelectro-stimulation device attached to a single point on the heart;

FIG. 6 shows operation of a foot pedal by a surgeon during heartelectro-stimulation;

FIG. 7 is a cross sectional view of a catheter and a set of electrodespositioned circumferentially around the catheter according to theinvention;

FIG. 8 is a cross sectional view of a catheter and a set of electrodespositioned circumferentially around the catheter according to a secondembodiment of the invention;

FIG. 9 is a side elevational view of a catheter with electrodespositioned axially along the catheter according to a third embodiment ofthe invention;

FIG. 10 is a side elevational view of a catheter with electrodespositioned axially along the catheter according to a fourth embodimentof the invention;

FIG. 11 is a top plan view of a catheter with electrodes positionedaxially along the catheter according to a fifth embodiment of theinvention;

FIG. 12 is a top plan view of a catheter with electrodes positionedaxially and circumferentially along the catheter according to a sixthembodiment of the invention;

FIG. 13 is a cross sectional view similar to FIG. 8 showing the currentdensity distribution between two of the electrodes;

FIG. 14 is a cross sectional view similar to FIG. 7 showing the currentdensity distribution between two of the electrodes;

FIG. 15 is a top view of a catheter with electrodes positioned axiallyand circumferentially along the catheter and showing the current densitydistribution between two of the electrodes.

FIG. 16 illustrates an embodiment of the invention as employed with animplantable cardiac pacemaker which also stimulates the vagal nerve totreat arrhythmias and/or angina.

FIG. 17 illustrates the present invention in an embodiment including anupper airway stimulator in which stimulation of the hypoglossal nerve isemployed to treat obstructive sleep apnea.

FIG. 18 illustrates an embodiment of the invention employed to stimulatethe phrenic nerve in order to provide a diaphragmatic pacemaker.

FIG. 19 illustrates an embodiment of the invention as employed inconjunction with an implantable cardioverter defibrillator in whichvagal nerve stimulation is employed to treat detected arrhythmias or toprevent arrhythmias.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a first embodiment of an electro-stimulationdevice 10 includes a housing 12 and a control panel 14 located on anupper surface of the housing 12. The control panel 14 is divided into aheart stimulation control area 15 and a heart destimulation control area17. The stimulation control area 15 includes a rotary dial 16 and scale16A for setting the amount of current that is passed to the heart, and arotary dial 18 and scale 18A for setting the duration or frequency ofcycles that the current is passed to the heart to start the heartbeating. Likewise, the destimulation control area 17 includes a rotarydial 20 and scale 20A for setting the amount of current that is passedto the heart, and a rotary dial 22 and scale 22A for setting theduration that the current is passed to the heart to stop the heart frombeating. Controls for regulating pulse width, pulse voltage, pulsephases and/or burst duration may also be added. A normally openstimulation switch 24 can be pressed to initiate heart stimulation whilea normally open destimulation switch 26 can be pressed to initiate theheart destimulation. An on/off switch 28 can be used to turn the entiredevice off when not in use.

A foot pedal assembly 30 has a normally open heart stimulation footswitch 32 and a heart destimulation foot switch 34 that can be used asan alternative to switches 24, 26. The provision of a foot pedalassembly permits the surgeon to control when the heart stimulation anddestimulation occurs while leaving the hands free to perform otherprocedures. This also permits the surgeon's hands to remain sterilesince contact with the housing 12 or switches 26, 28 is avoided. Thefoot pedal assembly 30 is connected via cable 36 to an electroniccontrol device 50 (FIG. 3) within the housing 12. An alternative toproviding two different foot switches 32, 34 would be to provide asingle foot switch which intermittently switches between stimulation anddestimulation each time the switch is actuated. It is also contemplatedthat automatic stimulation could be provided after a preset time periodor only if the device detects that the heart did not automaticallyrestart.

A pair of electrodes 37, 38 are connected via a pair of leads 39A, 39B,respectively, to the electronic control device 50 for supplyingelectrical current to the heart during stimulation and destimulation. Asecond pair of electrodes 43A, 45A can also be connected via a pair ofleads 43, 45, respectively, to the electronic control device 50 forsupplying electrical current to the phrenic nerve to control breathingduring heart stimulation and destimulation. A lead 48 having a connector49 may be provided in addition to or alternatively of the phrenic nerveelectrodes 43A, 43B. The connector 49 interfaces with a respirator (notshown) and, upon stimulation or destimulation of the heart, sends alogic signal to activate or deactivate the respirator.

Referring now to FIG. 2, a second embodiment of an electro-stimulationdevice 40 according to a second embodiment is shown, wherein like partsfrom the previous embodiment are represented by like numerals. Theelectro-stimulation device 40 is microprocessor based and includes ahousing 41 having a display 42, a plurality of numeric keys 44, a heartstimulation switch 46, and a heart destimulation switch 48. One of thekeys 44 may be an on/off switch for supplying electrical power to thedevice 40. The device 40 prompts a user to enter the patient's age,height, weight, body temperature, etc., via the keys 44 to calculate theproper amount of electrical current and its duration necessary forproper heart stimulation and destimulation. In most instances, theamount of current and duration to stop the heart will typically bedifferent than the amount of current and duration to start the heart,and will vary from one person to another depending on factors such asheight, weight, body temperature, etc. In the embodiments of FIGS. 1 and2, the current may be of the alternating, direct, or waveform type.

Referring now to FIG. 3, the electronic control device 50 for use withthe electro-stimulator of FIGS. 1 and 2 includes a regulated powersource 52, such as a battery and regulator, a stimulation timer circuit54, a destimulation timer circuit 55, a stimulation power amplifier 56,and a destimulation power amplifier 57. The timer circuits and poweramplifiers can be chosen from any of several well-known timers andamplifiers that can incorporate the dials 16, 18, 20, and 22. Thesedials may be of the variable resistive, capacitive, or pulse type tovary the timer frequency and power dissipation. Alternatively, inputfrom the keys 44 stored in a microprocessor 60 (shown in dashed line) inthe FIG. 2 embodiment can be used to vary the amplification and durationof the applied electrical current. The stimulation switch 24 andstimulation foot switch 32 on pedal assembly 30 are connected inparallel such that actuation of one or the other switch begins heartstimulation. Likewise, the destimulation switch 26 and stimulation footswitch 34 on pedal assembly 30 are connected in parallel such that theactuation of one or the other switch begins heart destimulation.Preferably, the switches are of the single-shot type that permit currentto flow through the circuit for the amount of time set by the timers 54,56, even when the switches are released. Alternatively, the switches maybe of the type requiring manual positioning between the open and closedpositions. In this alternative embodiment, the timers 54, 56 may providean audible signal to indicate when the appropriate duration ofelectrical current application has been reached. The timers 54, 56 mayalso be eliminated. In this instance, the appropriate switch is manuallyclosed until the surgeon visually observes that the heart has beenproperly stimulated or destimulated.

With reference now to FIG. 4, the electrode 37 is connected to thesinoatrial region 72 of heart 70 while the electrode 38 is connected tothe atrioventricular region 74 in a unipolar arrangement, while theelectrodes 43A, 43B are connected to the phrenic nerve (not shown) or toother regions of the body or heart. The separate connection regions onthe heart serve to alternatively stimulate and destimulate the heart.The electrode terminations may be of the type used in pacemakers, suchas corkscrews, clips, pads, tines or barbs, needles, etc. The electrodes37, 38 may both be connected to the ventricular wall as shown in FIG. 5in a bipolar arrangement or at any position that a pacemaker is commonlyconnected to. The electrodes 43A, 43B may be connected in a bipolararrangement to the vagus nerve or one of its cardiac branches. In thebipolar arrangement, the electrodes 37, 38 are placed near each other ata particular region for stimulating the heart while the electrodes 43A,45A are placed near each other at a second region for destimulating theheart. The tissue between each pair of serves to close the circuit suchthat electrical current from the power source and amplifier passesthrough the tissue to cause stimulation or destimulation of the heart.

When the electrodes are connected to other locations besides the heart,a series of current pulses is passed long enough through the tissue toaugment any recurring natural heartbeat stimuli to stop the heart frombeating. It has been found that a continuous pulse train for 10-30seconds using a constant current of 10-100 mA in conjunction with aconstant pulse width of 0.01-0.5 msec. and a frequency between 6 Hz and50 Hz applied to the epicardial parasympathetic nerves is sufficient toaugment the recurring natural heartbeat stimuli to stop the heart. Whenthe electrodes are connected directly to the heart, it is preferred thata burst pulse width of current be applied instead of a continuous pulsetrain. Once activity from the heart is sensed, a burst pulse widthhaving the same current amplitude and frequency as in the constant pulsewidth is applied during the repolarization phase. Typically, the burstpulse time will be less than the continuous pulse train to stop theheart. Preferably, the burst pulse is programmable for different bursttimes, current amplitudes, and frequency. Upon cessation of heartdestimulation, the natural heart beat stimuli will typically occur againautomatically a short time thereafter. The separate heart stimulationleads, therefore, provide an added safety feature in the event that theheart does not automatically restart. In order to stimulate the heart,if required, a series of current pulses are passed through the tissue toinitiate the natural heartbeat stimuli. These current pulses are similarto those used in pacemakers.

In use, the electrodes 37, 38 are secured at an appropriate position onthe patient 80 (FIG. 6). During open surgery or minimally invasivesurgery, as the surgeon 82 performs various steps such as cutting,stitching, etc., one of the foot switches 32, 34 is pressed to initiateor stop the heartbeat as required. For example, the surgeon may wish tostop the heartbeat while making one or a plurality of stitches wheremovement of the heart would normally be a hindrance. The heart may thenbe stimulated either naturally or artificially through the presentdevice to beat for a predetermined time to permit blood flow throughoutthe body and then be destimulated or stopped again to continuestitching. If desired, the electrodes 43A, 45A may be connected to thephrenic nerve and/or the connector 49 may be attached to a respirator tostill the lungs during the surgical procedure. When the electrodes areattached to the phrenic nerve, a continuous pulse train having the rangeof values as discussed previously is sufficient for controlling lungmovement.

Referring now to FIG. 7, and according to a further embodiment, a set offour electrodes 102, 104, 106, and 108 are equally circumferentiallyspaced around a catheter 100. Each electrode 102-108 is embedded in andextends from an inner wall 110 to an outer wall 112 of the catheter 100.A separate insulated lead 102a, 104a, 106a, and 108a are each solderedor otherwise electrically connected to their respective electrode. Theinsulated leads extend through the catheter 100 and into the electroniccontrol device 50. Any pair of electrodes can be accessed through extraswitches in the control device 50 for supplying electrical current tothe heart during stimulation and destimulation.

Referring now to FIG. 8, and according to a further embodiment, a set ofthree electrodes 122, 124 and 126 are equally circumferentially spacedaround a catheter 120. Each electrode 122-126 is embedded in and extendsfrom an inner wall 130 to an outer wall 132 of the catheter 120. Aseparate insulated lead 122a, 124a and 126a are each soldered orotherwise electrically connected to their respective electrode. As inthe previous embodiment, the insulated leads extend through the catheter100 and into the electronic control device 50. Any pair of electrodescan be accessed through extra switches in the control device 50 forsupplying electrical current to the heart during stimulation anddestimulation.

Although the catheters 100, 120 have been described with three or fourelectrodes, any number of electrodes may be provided, depending on theparticular nerve stimulation application. For example, as shown in FIG.9, two electrodes 142, 144 may be spaced axially on a catheter 140. Thelongitudinal centerline of each electrode 142, 144 extendsperpendicularly to the axis of the catheter 140.

In FIG. 10, two electrodes 152, 154 are spaced axially andcircumferentially from each other on the catheter 150. Theirlongitudinal centerlines extend parallel to the axis of the catheter.Two additional electrodes 156, 158 (shown in dashed line) may beprovided on an opposite side of the catheter 150, as shown in FIG. 11.

In yet another embodiment, as shown in FIG. 12, a first electrode 162 isspaced axially and circumferentially from a pair of circumferentiallyelectrodes 164, 166 on a catheter 160. Each of the electrodes 162-166extends approximately 120° around the circumference of the catheter 160.

The catheters 100-160 as shown in FIGS. 7-12 are preferably of a smallsize to fit easily into the internal jugular vein, superior vena cava orother appropriate vessel adjacent to the desired nerve bundle. Theinternal jugular vein is next to the vagal nerve bundle, and thuspresents an ideal path for the catheter when attempting to stimulate thevagal nerve. The human internal jugular vein is about 2 to 6 mm indiameter and tapers over an estimated length of about 15 cm. Hence, theuse of a 7 F or smaller size catheter is contemplated. The electrodesare placed on the catheter in such a way that the amplitude required tostimulate the nerve fibers would have the correct field distribution.For an internal jugular vein of about 5 mm in diameter and a vagal nervebundle of about 3 mm in diameter, and for an applied current of 10 mAwith a frequency of 2-20 Hz, the spacing between the electrodes wouldneed to be about 1-2 cm to achieve nerve stimulation. This spacing mayvary depending on the size of the internal jugular vein and vagal nervebundle, as well as the amount of applied current.

Referring now to FIG. 13, electrodes 104, 106 of the catheter 100 are incontact with a nerve (not shown) and have been selected to apply acurrent thereto. The circumferential current density through the nervetissue, as represented by lines 170, diminishes as the distanceincreases from the pair of activated electrodes. FIG. 14 shows a similaroccurrence for the three-electrode embodiment of FIG. 8. Since theelectrodes in this embodiment are spaced a greater distance than theelectrodes from in the FIG. 7 embodiment, the current distribution isnot as concentrated, and therefore produces a different neuralstimulation.

An axial current distribution may be required in addition to or in placeof the circumferential distribution, as shown in FIG. 15, depending onthe particular nerve stimulation desired. The axial current distributionis obtained by accessing a pair of axially spaced electrodes (FIG. 9) ora pair of axially and circumferentially spaced electrodes (FIGS. 10-12).

The preferred use of the electro-stimulation device would be atransvenous implementation through standard transvenous implantationtechniques such as those used to implant pace/sense leads into theheart. For the method of transvenous vagal stimulation inlaproscopic/endoscopic/minithorascopic surgical coronary artery bypassgraft (CABG) procedures, the use of vagal nerve stimulation provides areversible, quick acting (like an on/off switch) method for slowing theheart rate.

Although the foregoing description relates to thestimulation/destimulation of the heart during surgical procedures, it isnot intended that the invention be limited thereto. Theelectro-stimulation device could be provided with two or moreelectrode-wielding catheters for use in multiple transvenous regions forthe stimulation of different nerves. For example, a pair of catheterscould be inserted into the internal jugular vein for stimulation of theright and left vagal nerve bundles. The right bundle could be used toelicit more specific heart effects and reduce heart rate and increase AVdelay for antiarrhythmic and hemodynamic benefits; whereas the leftbundle could be used to effect afferent vagal information andpotentially reduce epileptic activity. An electrode-wielding cathetercould be inserted into the very high internal jugular vein to stimulatethe hypoglossal nerve and/or into the very low internal jugular vein orsuperior vena cava to stimulate the phrenic nerve for respiratorycontrol. The stimulation of the phrenic nerve in conjunction with heartstimulation would insure that the blood is properly oxygenated duringsurgical procedures on the heart with intermittent heart destimulation.Likewise, catheters of the present invention could be inserted into theazygos or accessory hemizygous veins to stimulate the sympathetic nervesfor increasing heart rate or altering DFT efficacy for antiarrhythmicand hemodynamic benefits. Other transvenous routes to nerve stimulationfor functional purposes may also be applicable.

The electro-stimulation device may also have specificity for directionof neural stimulation in regards to the location of the vessel and thenerve bundle that is to be stimulated. For example, the phrenic nervecould be elicited on and off by a mere rotation of the transvenouscatheter, depending on the location of the electrodes on the catheterand the resulting electric current density generated. In order toobserve and control the amount of catheter rotation, a series of degreemarkings may be located on an outer circumference of the catheter at aposition readily observable by the surgeon. Alternatively, the cathetermay be associated with a rotary encoder to obtain a digital read-out ofthe amount of catheter rotation.

The electrodes of the intravenous catheters according to the presentinvention could also be used to manipulate the heart rate orhemodynamics in response to device sensors. In addition, in response toprecursors of an arrhythmic event, the device may stimulate either thesympathetic or the parasympathetic individually or in combination toattempt to delay or prevent the event. Alternatively, current may beapplied to different pairs of electrodes as discussed above.

Although the use of catheters having electrodes permanently mountedthereto for temporarily manipulating or stimulating nerves accessiblethrough blood carrying vessels, it is to be understood that a morepermanent nerve stimulation arrangement is possible by fixing electrodesonto the inside of the vessel adjacent to the nerve to be stimulated.Thus, this new device in its preferred embodiment eliminates thepotential for direct nerve damage and reduces the invasiveness of theplacement of the electrodes for direct neural stimulation in conjunctionwith implantable medical devices. Examples of how the present inventionmay be employed in the context of implantable medical devices areillustrated in FIGS. 16-19.

FIG. 16 illustrates an embodiment of the present invention employing apermanently implantable cardiac pacemaker 300 coupled to an electrodelead 304 used to stimulate the vagal nerve in accordance with thepresent invention. The pacemaker is also provided with a secondelectrical lead 308, which, like electrical lead 304 is coupled to thecircuitry within the housing of pacemaker 300 by means of a connectorblock 302. Pacemaker 300 includes therein both a dual chamber cardiacpacemaker and an implantable nerve stimulator, and may correspond tothat illustrated in U.S. Pat. No. 5,334,221 issued to Bardy; U.S. Pat.No. 5,330,507 issued to Schwartz or U.S. Pat. No. 5,199,428 issued toObel et al, all of which are incorporated herein by reference in theirentireties.

Electrode lead 304 has an array of electrodes as illustrated in FIGS.7-15, discussed above, located at or adjacent its distal end 306 whichis positioned within the internal jugular vein 316, with electrodeschosen to direct the stimulation pulses provided by the electrodes tothe vagal nerve in order to slow heart rate. The second electrode lead308 carries a pair of electrodes 310 for sensing depolarizations of theatrium of the patient's heart and a pair of electrodes 312 for sensingand pacing the ventricle of the patient's heart. As described in theabove cited patents, the electrodes on lead 304 may be employed to slowthe patients heart rhythm in order to prevent or treat detectedarrhythmias, ischemia, angina or other problems. The electrodes 310 and312 may be employed to sense the rate of the heart and to ensure thatthe heart is beating at an adequate rate, preventing overstimulation ofthe vagal nerve from causing the heart to drop below a base heart ratedetermined either as a fixed parameter or as a function of an indwellingactivity sensor within pacemaker 300. Electrode lead 304 may be formedwith a bend 318, preformed into the body of the lead a distance from theelectrode array the distal end of the lead 306 to position itappropriately for vagal nerve stimulation. The lead may be inserted andpositioned generally according to the procedure disclosed in U.S. Pat.No. 5,354,318 issued to Taepke, describing a similarly located andconfigured lead, also incorporated herein by reference in its entirety.

FIG. 17 illustrates an embodiment of the invention in which an implantedstimulator 400 is used in conjunction with an electrode lead accordingto the present invention to stimulate the hypoglossal nerve to treatobstructive sleep apnea. The pulse generator may correspond to thatdisclosed in U.S. Pat. No. 5,549,655 issued to Erickson and incorporatedherein by reference in its entirety. The stimulator 400 is provided witha first electrode lead 404 which carries adjacent its distal end 406 anarray of electrodes as described in FIGS. 7-15, discussed above. Thelead is located relatively higher up within the internal jugular arterythan the electrode array in FIG. 16 and is directed to stimulate thehypoglossal nerve by selection of appropriate electrodes as describedabove. Like the lead 304 described in FIG. 16, lead 404 may optionallybe provided with a preformed bend 414, an appropriate distance from thelocation of the electrode array the distal end 406 of the catheter toposition it in appropriate position and orientation to stimulate thehypoglossal nerve. The lead, like lead 304 in FIG. 16, may be insertedaccording to the procedure described in U.S. Pat. No. 5,354,318 issuedto Taepke. The pulse generator 400 is additionally provided with asecond lead 408 which carries a pressure sensor 410 which is used tosynchronize delivery of hypoglossal nerve stimulus pulses to thedetected inspiratory phase of the respiration cycle as described in theabove cited Erickson patent.

FIG. 18 illustrates an additional embodiment of the present inventionincluding a pulse generator 500 employed to stimulate the phrenic nervein order to provide a diaphragmatic pacer. Pacer 500 may correspondgenerally to that disclosed in U.S. Pat. No. 5,056,519, issued to Vinceet al. which employs a signal indicative of the normal respirativefunction of the right diaphragm to regulate stimulation of the leftphrenic nerve to correspondingly stimulate the left diaphragm. A pulsegenerator 500 is provided with a second lead 508 which carries at itsdistal tip a temperature sensor 510 which is employed to sense thetemperature changes within body tissues resulting from inspiration ofoutside air through the upper airways. Temperature sensor 510 may belocated within the airway to the right diaphragm as described in theVince patent and employed to regulate stimulus pulses provided to theelectrodes on lead 504 so that the left diaphram functions in synchronywith the inspiratory cycle of the right diaphram. Lead 504 may beprovided with a preformed bend 514 located an appropriate distance fromthe electrode array located at the distal end of 506 of the lead toposition the electrode array adjacent the phrenic nerve. The lead may beintroduced using the procedure described in the above cited Gundersonpatent.

FIG. 19 illustrates an embodiment of the invention employed inconjunction with an implantable cardioverter/defibrillator 600 whichemploys vagal nerve stimulation as an adjunct to its array ofantitachyarrhythmia therapies including antitachyacardia pacing,cardioversion and defibrillation. Pulse generator 600 may correspond,for example, to the pulse generator illustrated in U.S. Pat. No.5,014,698 issued to Collins or U.S. Pat. No. 5,243,980 issued to Mehra,both incorporated herein by reference in their entireties.

Pulse generator 600 is provided with an electrical lead 604 whichcarries adjacent its distal end 606 an array of electrodes as describedin conjunction with FIGS. 7-14 above. Electrode lead 604 may correspondto electrode lead 304 illustrated in FIG. 15, with its distal end 606located within the internal jugular vein in a position appropriate tostimulate the vagal nerve. The pulse generator 600 is also provided witha second electrode lead 608 which carries first and seconddefibrillation electrodes 610 and 612 and pacing/sensing electrodes 614and 616 which are employed to sense and pace the ventricle of thepatient's heart. The vagal nerve stimulator may be employed inconjunction with delivery of therapies of treatment of arrhythmias orprevention of arrhythmias as described in the above cited Collins et alpatent or may be employed as part of a diagnostic regimen as describedin the above cited Mehra patent.

The embodiments of the invention illustrated in FIGS. 16-19 above areintended to be exemplary of general types of devices in which thepresent invention may be employed by transvenously locating an electrodeor array of electrodes in a blood vessel adjacent a desired nerve to bestimulated, as discussed above. It should be understood that permanentlyimplanted leads configured and located according to the presentinvention may be used with a wide variety of implantable electricaldevices not specifically illustrated in conjunction with FIGS. 16-19,including implantable drug dispensers, implantable muscle or nervestimulators, and implantable monitoring systems in which regulation ofone or more nervous functions is desired. It should also be understoodthat in conjunction with such devices, as discussed above, electrodesmay be located bi-laterally, and employed to stimulate the same ordifferent nerves, also as discussed above.

Reasonable variation and modification are possible within the spirit ofthe foregoing specification and drawings without departing from thescope of the invention.

The embodiments for which an exclusive property or privilege is claimedare defined as follows:
 1. A method for stimulating desired nerve fiberswithin a living body, comprising the steps of:advancing a lead carryingan array of electrodes through the vascular system to a point within avein adjacent the nerve fibers to be stimulated; selectively employingelectrodes within the array to direct electrical pulses applied to theelectrodes to the desired nerve fibers; and delivering electrical pulsesto the selectively employed electrodes.
 2. A method for stimulatingdesired nerve fibers within a living body, comprising the stepsof:advancing a lead carrying electrodes through the vascular system to apoint within an internal jugular vein adjacent the nerve fibers to bestimulated; employing electrodes to direct electrical pulses applied tothe electrodes to the desired nerve fibers; and delivering electricalpulses to the employed electrodes.
 3. A method according to claim 1 orclaim 2 wherein said advancing step comprises advancing said lead toposition said electrodes adjacent vagus nerve fibers.
 4. A methodaccording to claim 1 or claim 2 wherein said advancing step comprisesadvancing said lead to position said electrodes adjacent hypoglossalnerve fibers.
 5. A method according to claim 1 or claim 2 wherein saidadvancing step comprises advancing said lead to position said electrodesadjacent phrenic nerve fibers.
 6. A method according to claim 1 whereinsaid advancing step comprises advancing said lead to position saidelectrodes within an azygous vein.
 7. A method according to claim 1wherein said advancing step comprises advancing said lead to positionsaid electrodes within a hemizygous vein.
 8. A method according to claim1 wherein said advancing step comprises advancing said lead to positionsaid electrodes adjacent parasympathetic nerve fibers.
 9. A methodaccording to claim 1 wherein said advancing step comprises advancingsaid lead to position said electrodes adjacent sympathetic nerve fibers.10. An apparatus for stimulating desired nerve fibers within a livingbody, comprising:a transvenous lead carrying an array of electrodeslocatable in the vascular system at a point within a vein adjacent thenerve fibers to be stimulated; switch means for selectively employingelectrodes within the array to direct electrical pulses applied to theelectrodes to the desired nerve fibers; and pulse generator means fordelivering electrical pulses to the selectively employed electrodes. 11.An apparatus according to claim 10 wherein said array is locatable in apatients internal jugular vein adjacent the patient's vagus nerve, andwherein said device further comprises cardiac pacing means forstimulating heartbeats following delivery of pulses to the electrodearray.
 12. An apparatus according to claim 10 or claim 11 furthercomprising phrenic nerve stimulation electrodes locatable adjacent thepatients phrenic nerve and means for delivering electrical pulses to thephrenic nerve stimulation electrodes in conjunction with delivery ofpulses to the electrode array.